JP3273667B2 - Method for producing melt-blown thermoplastic nonwoven fabric - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an manufacturing how meltblown thermoplastic resin nonwoven fabric, there is little variation in fiber diameter, and good meltblown thermoplastic resin <br/> production side of the nonwoven fabric drapability About the law.

[0002]

[0003]

2. Description of the Related Art In recent years,
Nonwoven fabrics have been used in a wide range of fields such as air filter materials and liquid filter materials, and their production has been increasing.

A typical non-woven fabric used for such a filter is a melt-blown thermoplastic non-woven fabric.
Melt blown thermoplastic nonwoven fabric extrudes molten thermoplastic resin from a die with many orifices, stretches it by blowing out high-temperature, high-speed airflow, deposits fine fibrous material, and forms a web. It is made.

[0005] Such a melt-blown thermoplastic resin non-woven fabric generally has a fine representative average fiber diameter. However, for a filter material such as an air filter material, it is better to use a thick fiber for a pressure loss. Can be lowered,
Usually, the fiber has a typical average fiber diameter of 8 μm or more. However, melt-blown thermoplastic nonwovens are
If the fiber diameter is somewhat large, the heat capacity of the spun fiber increases, and the solidification rate slows down.Therefore, the fibers constituting the nonwoven fabric are widely fused together, and apparently it is easy to form one very thick fiber. Become. For this reason, the apparent fiber diameter becomes extremely large with respect to the actual single fiber diameter, and the apparent fiber diameter constituting the nonwoven fabric varies, so that the basis weight distribution of the nonwoven fabric increases.
In addition, for the reasons described above, when a melt-blown thermoplastic resin nonwoven fabric is used for an air filter or the like, there is a problem in that dust collection efficiency varies, and a highly reliable air filter cannot be obtained. .

On the other hand, the melt-blown thermoplastic resin non-woven fabric in which the respective fibers are fused widely as described above has a problem that the apparent fiber diameter of the fibers constituting the non-woven fabric is large, so that it is hard and the drape property is inferior. There is.

[0007] Accordingly, an object of the present invention is to provide a method for dispersion of the fiber diameter is small and the production of drapability good meltblown thermoplastic resin nonwoven fabric.

[0008]

[0009]

Means for Solving the Problems As a result of intensive studies in view of the above object, the present inventors found that the large dispersibility of the fiber diameter of the melt-blown thermoplastic resin non-woven fabric is due to the fact that the fibers are fused in a wide range. This is because the apparent fiber diameter becomes significantly larger than the actual single fiber diameter. It has been found that a melt-blown thermoplastic resin nonwoven fabric having good collection efficiency, high reliability, and good drapability can be obtained. Thus, the present inventors have studied such a method for producing a melt-blown thermoplastic resin nonwoven fabric, and found that the diameter of the nozzle of the orifice and the distance between the edges of the orifice are the desired average of the melt-blown thermoplastic nonwoven fabric. The fiber diameter (d: mode average value) is set so as to have a specific relationship, and the temperature (T) of the nozzle of the orifice and the air temperature (t) used are determined according to the melting point (mp) of the resin and the desired temperature. It has been found that the melt-blowing method may be performed by setting a specific relationship with the representative average fiber diameter (d).
The present invention has been made based on the above findings.

[0010]

[0011] That is, manufacturing how meltblown thermoplastic resin nonwoven fabric of the present invention, diameter of the nozzle orifice meltblowing apparatus: and (D mm), the orifices of the distance between the edges: the (L mm), the orifice of the nozzle Temperature (T:
° C) and the air temperature used (t: ° C) are expressed by the following formula with respect to the melting point of the resin (mp: ° C) and the desired average fiber diameter (d: µm) of the desired melt-blown thermoplastic resin nonwoven fabric: 10 ≦ d / D ≦ 20, characterized in that setting 0.1 ≦ D ² /(L+D)≦0.3, respectively so as to satisfy 50 ≦ T-mp ≦ 200 and 0.2 ≦ (T-t) / d 2 ≦ 1.0, And

[0012]

The present invention will be described in detail below. [1] As the thermoplastic resin constituting the meltblown thermoplastic resin nonwoven fabric main Rutoburo thermoplastic resin nonwoven fabric is not particularly limited as long as it can apply a meltblowing, polyethylene, polyolefins such as polypropylene, polyethylene terephthalate, poly Examples thereof include polyesters such as butylene terephthalate, polyamides such as nylon 6, nylon 66, and nylon 46, polyvinyl chloride, polyvinylidene chloride, polystyrene, polycarbonate, and polyvinylidene fluoride. Of these, polyolefins and polyesters are preferred. These thermoplastic resins can be appropriately blended and used as needed.

Using such a thermoplastic resin , the present invention
The melt-blown thermoplastic resin nonwoven fabric obtained by the production method has the following physical properties. (1) The apparent fiber diameter is 6 to 40 μm, preferably 8 to 25 μm
m. (2) The dispersibility of the fiber diameter is 50 to 100%, preferably 75 to 100
%. (3) The basis weight is 10 to 300 g / m ² , preferably 30 to ²⁰⁰ g / m ²
m ² . (4) The basis coefficient of variation (CV value) is 9% or less, preferably 6% or less.

The apparent fiber diameter refers to an indirect fiber diameter obtained from the basis weight, thickness, and air permeability. Apparent fiber diameter
If it exceeds 40 μm, the basis weight CV value described later becomes large, and the reliability of the filter becomes low. The lower limit is 6 μm.

The dispersibility of the fiber diameter is defined as the ratio of fusion between the single fibers constituting the web and the dispersibility of the single fibers (
(Air permeability at an area of 40 mmφ / air permeability at an area of 70 mmφ) ×
(7/4) ² × 100 (%)). When the dispersibility of the fiber diameter is less than 50%, the basis weight CV value becomes poor, and the reliability as a filter material decreases.

The weight coefficient of variation (CV value) of the basis weight is a scale indicating the variation of the basis weight, and is statistically calculated by (standard deviation in the direction of the basis weight / average value) × 100 (%). Value. If the CV value exceeds 9%, the reliability as a filter decreases.

In the present invention, the term "representative average fiber diameter" refers to an average fiber diameter based on a mode average value when groups of apparent fiber diameters are divided at substantially equal intervals on a logarithmic scale.

[2] Production Method Next, a method for producing the melt-blown thermoplastic resin nonwoven fabric of the present invention will be described.

First, a nonwoven fabric is manufactured from a thermoplastic resin.
The nonwoven fabric is manufactured by the melt blow method as described above. FIG. 1 shows an example of an apparatus for producing a nonwoven fabric by a melt blowing method. In FIG. 1, the melt blow molding apparatus includes an extruder 1, a hopper 3 for supplying a thermoplastic resin to the extruder 1, a motor 4 for rotating a screw (not shown) of the extruder 1, and a tip of the extruder 1. And the die 2 provided in the The die 2 has a number of fine orifices 11 arranged in a row, slits 12 and 13, and heated gas transport pipes 14 and 15.
And heaters 16 and 17.

FIG. 2 is an enlarged sectional view of the die 2 shown in FIG. The die 2 includes an upper die plate 21, a lower die plate 22, an upper gas plate 23, and a lower gas plate.
Consists of 24. By combining such components, the orifice 11, the slits 12 and 13, and the upper air chamber 25 and the lower air chamber 26 communicating with the slits 12 and 13 are formed. Orifice 11
It has a rear end, a middle part, and a front end. An inlet 27 made of a thermoplastic resin is connected to the rear end. A middle part is a resin chamber 28, and a front end is a nozzle part 29. Heated gas transport pipes 14 and 15 are connected to the upper air chamber 25 and the lower air chamber 26, respectively. The upper die plate 21 and the lower die plate 22 include a heater 16 for maintaining the orifice 11 at a temperature described later.
17 are buried.

In such a blow molding apparatus, the thermoplastic resin is supplied from the hopper 3 to the extruder 1, melted and kneaded, and then discharged from the inlet 27 through the resin chamber 28 through the nozzle 29. At the same time, gas such as heated air supplied from the heated gas transport pipes 14 and 15 is injected from the slits 12 and 13 at a high speed, and the discharged molten thermoplastic resin is miniaturized. The fiber stream 5 generated here is accumulated on a collecting surface such as a rotating collector roll 6, and a nonwoven fabric 7 is formed .

In the present invention, the diameter (D: mm) of the nozzle 29 of the orifice 11 and the distance between the orifices (the distance between the edges of the orifice 11 (L: mm)) of the apparatus for manufacturing a melt-blown thermoplastic nonwoven fabric are described. ) And the desired average fiber diameter of the desired melt-blown thermoplastic resin nonwoven fabric (d:
μm, mode average value), the following relational expression (1) and
(2) Set each to satisfy. 10 ≦ d / D ≦ 20 (1) 0.1 ≦ D ² /(L+D)≦0.3 (2)

In the present invention, the temperature of the orifice 11 (T: ° C.) and the temperature of the blow air to be used (t: ° C.) are determined by the melting point (mp: ° C.) of the resin to be used and the representative of the melt-blown thermoplastic nonwoven fabric. The average fiber diameter (d: μm) is set so as to satisfy the following relational expressions (3) and (4). 50 ≦ T-mp ≦ 200 (3) 0.2 ≦ (Tt) / d ² ≦ 1.0 (4)

If the temperature of the orifice 11 is lower than the melting point of the resin + 50 ° C., the resin solidifies too quickly, so that even if the fibers are entangled, the fibers are not fused at the entangled point, and the strength of the obtained nonwoven fabric is reduced. On the other hand, if the melting point of the resin exceeds 200 ° C., the single fibers are fused together in a wide range, and the dispersibility of the fiber diameter becomes large. In addition, the temperature (t) of the blow air is determined by the above equation.
If the temperature is lower than the range satisfying (4), the resin solidifies too quickly, so that even if the fibers are entangled, the fibers are not fused at the entangled point, and the strength of the obtained nonwoven fabric is reduced. On the other hand, the above relational expression
If it is higher than the range satisfying (4), the single fibers are fused together in a wide range, and the dispersibility of the fiber diameter becomes large.

For example, when polypropylene is used as the resin and the fiber diameter of the desired nonwoven fabric is 15 μm, the temperature of the orifice 11 is set to 280 to 350 ° C., and the temperature of the air used is set to 18 ° C.
Set to 0 to 260 ° C. Representative average fiber diameter 15μm
When producing a nonwoven fabric consisting of a single fiber of
Diameter of 0.3-0.5 mm, orifice 11 temperature 280-35
Usually, the temperature is 0 ° C and the air temperature used is 280-330 ° C. As described above, in the present invention, the nozzle diameter and the distance between orifices are set as described above, and the air temperature used is set to 180 to 260 ° C., which is lower than the conventional one. There is no fusion in the range.

[0027] This way is to give Rume Rutoburo thermoplastic resin nonwoven fabric, a crosslinking agent if necessary, surfactants, antistatic agents, processing can be performed by various additives such as flame retardants. The or main Rutoburo thermoplastic resin nonwoven fabric, it is possible to perform subsequently raising treatment needed, press working or the like, various processes.

[3] Electret nonwoven fabric In the present invention, the thermoplastic resin thus obtained is
An electret thermoplastic resin nonwoven fabric can be obtained by subjecting the oily nonwoven fabric to electret processing.

[0029] There is no particular limitation on the method of an electret processed, it can be performed according to conventional methods. For example, by colliding electrified particles with the flow of fine fibers extruded from the orifice, the fibers are accumulated on the collection surface,
Examples of the method include simultaneous production of a nonwoven fabric and electretization, and a method of first producing a nonwoven fabric and then applying a high DC voltage to the nonwoven fabric.

The applied voltage includes the basis weight, the fiber diameter, the filling rate,
The material constituting the nonwoven fabric, the distance between the electrodes, etc. varies, but when the distance between the electrodes is 5 to 30 cm, 5 to 30 kV, especially
It is preferably set to 10 to 20 kV.

The electret nonwoven fabric thus obtained usually has a charge of about 10 ⁻¹¹ to 10 ⁻⁷ coulomb / cm ² .

[0032]

[Action] manufacturing meltblown thermoplastic resin nonwoven fabric of the present invention
The manufacturing method is such that the diameter of the nozzle of the orifice and the distance between the edges of the orifice have a specific relationship with the desired average fiber diameter (d: mode average value) of the desired melt-blown thermoplastic nonwoven fabric. and sets, cage
The temperature (T) of the nozzle of the fiss and the air temperature (t) to be used satisfy a specific relationship between the melting point (mp) of the resin to be used and the representative average fiber diameter (d) of the melt-blown thermoplastic resin nonwoven fabric. Melt blow molding is performed in such a manner that the obtained nonwoven fabric has a typical average fiber diameter of 7 to 40 μm, has a small dispersibility in the fiber diameter, and has good drapability.

The reason why such an effect is obtained is not necessarily clear, but is considered as follows. That is, the dispersibility and drapability of the fiber diameter of the melt blown fiber having a relatively large representative average fiber diameter are inferior because the heat capacity of the spun fiber becomes large and the solidification speed becomes slow, so that the fibers are spread over a wide range. This is due to fusion. Therefore, in the present invention, the diameter of the nozzle of the orifice and the distance between the edges of the orifice are made larger than before, and the blow air temperature is lowered.
The fibers are cooled rapidly, and the single fibers are fused at the entanglement point during spinning, but are not fused over a wide range. Therefore, the basis CV value can be reduced to 9% or less.

The method of the present invention is also useful.
The obtained melt blown thermoplastic resin nonwoven fabric subjected to electret processing has a good collection efficiency and is highly reliable as a filter material. This is because the dispersibility of the fibers constituting the non-woven fabric is small, so that the charge amount can be imparted uniformly when electret processing is performed, and the unevenness of the gap formed between the single fibers is small, so that the particles to be captured It is considered that there is no omission.

[0035]

The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto.

Examples 1 to 3 and Comparative Examples 1 to 3 Using the melt blow apparatus ( having various configurations shown in Table 1) illustrated in FIG . A melt-blown thermoplastic nonwoven fabric of polypropylene (melting point: 160 ° C.) having a fiber diameter, a basis weight, and the number of laminated layers was produced under the conditions shown in Table 1.

The melt-blown thermoplastic resin nonwoven fabric was evaluated for fiber diameter dispersibility, basis weight CV value, drapability, and collection efficiency. The results are shown in Table 2.

The melt-blown thermoplastic resin non-woven fabric thus obtained was applied with an applied voltage of 12 kV and a distance between electrodes of 12 cm.
To make an electret . Electret heat obtained
The collection efficiency of the plastic resin nonwoven fabric was measured. The result is the amount of charge,
Table 2 shows the collection efficiency of the untreated nonwoven fabric.

[0039]

[0040]

(1) Nozzle diameter (D): The unit is mm. (2) Distance between edges (L): The unit is mm. (3) Orifice temperature (T): The unit is ° C. (4) Air temperature (t): The unit is ° C.

[0042]

[0043]

(1) Apparent fiber diameter: unit is μm. (2) Representative average fiber diameter (d): unit is μm. (3) Dispersibility of fiber diameter: (air permeability at area 40 mmφ / area 70
It was calculated by (air permeability in mmφ) × (7/4) ² × 100 (unit is%). (4) Basis weight: unit is g / m ² . (5) CV value of basis weight: (standard deviation in the direction of basis width / average value)
× 100 (unit is%). (6) Drapability: The nonwoven fabric obtained was evaluated as ○ when the touch was supple, and evaluated as × when it was not. (7) Collection efficiency: 0.3 μm NaCl particles, dust concentration 0.
At 5 mg / m ² and a surface wind speed of 5.3 cm / S, the collection efficiency was calculated by the light scattering method ((inflow side dust concentration−outflow side dust concentration) / inflow side dust concentration × 100) (unit:%).

[0045]

As described in detail above, the method for producing a melt-blown thermoplastic resin nonwoven fabric of the present invention can be achieved by increasing the diameter of the nozzle of the orifice and the distance between the edges of the orifice and by lowering the blow air temperature. ,
While preventing the filaments each other spun is fused over a wide range, it is possible meltblown molding obtained Mel
The blown thermoplastic nonwoven fabric has a relatively large representative average fiber diameter, a small fiber diameter dispersibility and a small CV value, and has good drapability.

[0046] It or Mel <br/> Toburo thermoplastic resin nonwoven fabric obtained by the production method of the present invention with electret
Rue electret nonwoven which has a good collection efficiency, reliable as a filter material.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example of a blow molding apparatus for producing a melt-blown thermoplastic resin nonwoven fabric of the present invention.

FIG. 2 is an enlarged sectional view of the die in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Extruder 2 ... Die 3 ... Hopper 4 ... Motor 5 ... Fiber flow 6 ... Collector roll 7 ... Nonwoven fabric 11 ... Orifice 12, 13 ... Slit 14, 15 ... heated gas transport pipe 16, 17 ... heater 21 ... upper die plate 22 ... lower die plate 23 ... upper gas plate 24 ... lower gas plate 25 ... upper Air chamber 26 ・ ・ ・ Lower air chamber 27 ・ ・ ・ Inlet 28 ・ ・ ・ Resin chamber 29 ・ ・ ・ Nozzle

Continuation of front page (56) References JP-A-4-163353 (JP, A) JP-A-1-156561 (JP, A) JP-A-63-6107 (JP, A) JP-A-6-257065 (JP) , A) (58) Fields investigated (Int. Cl. ⁷ , DB name) D04H 1/00-18/00

Claims (1)

(57) [Claims] (1) After melting and heating a thermoplastic resin, the nozzle is turned off.
Discharge from the orifice and check whether it is near the open end of the orifice.
Spraying heated gas from the nozzle to blow the molten resin flow
The method of manufacturing a meltblown thermoplastic non-woven fabric comprising the step of comminution Te, diameter of the nozzle orifice meltblowing apparatus: and (D mm), the distance between the orifice edge (L: mm) and, in the nozzle orifice temperature ( T: ° C)
And the operating air temperature (t: ° C.), and the melting point (m
p: ° C.) and the desired average fiber diameter (d: μm) of the desired melt-blown thermoplastic resin nonwoven fabric, the following formulas: 10 ≦ d / D ≦ 20, 0.1 ≦ D ² /(L+D)≦0.3, A method for producing a melt-blown thermoplastic resin nonwoven fabric, wherein the melt-blown thermoplastic resin nonwoven fabric is set so as to satisfy 50 ≦ T-mp ≦ 200 and 0.2 ≦ (Tt) / d ² ≦ 1.0.